Question 225098
Okay, set up the two given equations:
{{{Q+D=30}}}
{{{.25Q+.1D=4.50}}}
Solve the first one for one of the variables:
{{{Q=30-D}}}
Plug this into the second equation:
{{{.25(30-D)+.1D=4.5}}}
Simplify:
{{{30/4-.25D+.1D=4.5}}}
Combine like terms:
{{{30/4-.15D=4.5}}}
Subtract the {{{30/4}}} from both sides:
{{{-.15D=-3}}}
Divide both sides by -.15:
{{{D=20}}}
So, we have 20 dimes.
Since we know that {{{Q=30-D=30-20=10}}}
So, 10 quarters.
Checking our work, 20 dimes = $2 and 10 quarters = $2.5. The sum of those two gives us $4.5, so we're correct. Yay!
:-)